Absorbent article with low cold flow construction adhesive

ABSTRACT

Absorbent articles comprising a low cold flow construction adhesive suitable for joining at least two absorbent article components together, wherein the adhesive comprises an ethylene-based polyolefin resin and a crystallization enhancer, wherein at least one of the absorbent article components comprises a nonwoven material, and wherein the absorbent articles have an in-bag compression opening force of less than about 0.75N. Also, a method for assembling such articles.

FIELD OF THE INVENTION

This invention relates to the adhesive material, typically a hot meltadhesive, that is used to assemble components into an absorbent articlesuch as diaper (i. e. the construction adhesive). In particular thisinvention relates to such absorbent articles assembled using aconstruction adhesive that has reduced flowability when cold (i. e. attemperatures less than about 40° C.).

BACKGROUND OF THE INVENTION

Users, for example caregivers of infants, rely on disposable absorbentarticles to make their lives easier. Disposable absorbent articles, suchas adult incontinence articles and diapers, are generally manufacturedby combining several components. These components typically include aliquid-permeable topsheet; a liquid-impermeable backsheet attached tothe topsheet; and an absorbent core located between the topsheet and thebacksheet. When the disposable article is worn, the liquid-permeabletopsheet is positioned next to the body of the wearer. The topsheetallows passage of bodily fluids into the absorbent core. Theliquid-impermeable backsheet helps prevent leakage of fluids held in theabsorbent core. The absorbent core generally is designed to havedesirable physical properties, e.g. a high absorbent capacity and highabsorption rate, so that bodily fluids can be transported from the skinof the wearer into the disposable absorbent article.

Frequently one or more components of a disposable absorbent article areadhesively bonded together. For example, adhesives have been used tobond individual layers of the absorbent article, such as the topsheetand backsheet together. Adhesives have also been used to bond discretecomponents, such as fasteners and leg elastics or cuffs, to the article.The adhesive is often called a construction adhesive because it is usedto help construct the absorbent article from individual components.

In many instances, a hot-melt adhesive, i.e. a polymeric formulationthat is heated to substantially liquefy the formulation prior toapplication to one or both materials when making a laminate, is used asa construction adhesive. While such formulations generally work, theycan be costly and their performance properties can be improved. Forexample:

-   -   It is desirable that the adhesive remain in its intended        location after the absorbent article has been assembled and not        flow when “cold” (i. e. at normal ambient conditions of less        than about 40° C.). Such “cold flow” has been found to result in        undesirable adhesion between surfaces of the absorbent article        that are not intended to adhere to each other (e. g. a portion        of the topsheet in a diaper that has been folded for packaging        may adhere to another facing portion of the topsheet).    -   Such adhesives also have a desirable “open time” (i. e. the time        when the hot melt adhesive is at a high enough temperature that        it can join one material to another. If open time is too short,        the adhesive is not suitable as a construction adhesive because        components cannot be reliably assembled. If open time is too        long the adhesive may transfer from the assembled components of        the absorbent article to components of the production line with        resulting hygiene issues.        Thus, there is a continuing need for improved construction        adhesives for use in absorbent articles and the production        thereof.

SUMMARY OF THE INVENTION

The present invention is a disposable absorbent article that isassembled from a collection of components using a low cold flowconstruction adhesive. The construction adhesive comprises a polyolefinresin combined with an effective amount of a crystallization enhancer.The adhesive is maintained at a temperature from about 100° C. to about230° C. before application. The absorbent articles have an in bagcompression opening force of less than about 0.75N. The invention alsocomprises a method of producing the absorbent articles from a low coldflow construction adhesive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an exemplary diaper in a flat, uncontractedstate.

FIG. 2 is a stress/strain curve of opening force for the absorbentarticles of the Example.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the following terms shall have the meaning specifiedthereafter: “Disposable,” in reference to absorbent articles, means thatthe absorbent articles are generally not intended to be laundered orotherwise restored or reused as absorbent articles (i.e., they areintended to be discarded after a single use and, preferably, to berecycled, composted or otherwise discarded in an environmentallycompatible manner).

“Absorbent article” refers to devices which absorb and contain bodyexudates and, more specifically, refers to devices which are placedagainst or in proximity to the body of the wearer to absorb and containthe various exudates discharged from the body. Exemplary absorbentarticles include diapers, training pants, pull-on pant-type diapers(i.e., a diaper having a pre-formed waist opening and leg openings suchas illustrated in U.S. Pat. No. 6,120,487), refastenable diapers orpant-type diapers, incontinence briefs and undergarments, diaper holdersand liners, feminine hygiene garments such as panty liners, absorbentinserts, and the like.

“Proximal” and “Distal” refer respectively to the location of an elementrelatively near to or far from the longitudinal or lateral centerline ofa structure (e.g., the proximal edge of a longitudinally extendingelement is located nearer to the longitudinal centerline than the distaledge of the same element is located relative to the same longitudinalcenterline).

“Body-facing” and “garment-facing” refer respectively to the relativelocation of an element or a surface of an element or group of elements.“Body-facing” implies the element or surface is nearer to the wearerduring wear than some other element or surface. “Garment-facing” impliesthe element or surface is more remote from the wearer during wear thansome other element or surface (i.e., element or surface is proximate tothe wearer's garments that may be worn over the disposable absorbentarticle).

“Longitudinal” refers to a direction running substantially perpendicularfrom a waist edge to an opposing waist edge of the article and generallyparallel to the maximum linear dimension of the article. Directionswithin 45 degrees of the longitudinal direction are considered to be“longitudinal”

“Lateral” refers to a direction running from a longitudinal edge to anopposing longitudinal edge of the article and generally at a right angleto the longitudinal direction. Directions within 45 degrees of thelateral direction are considered to be “lateral.”

“Disposed” refers to an element being located in a particular place orposition.

“Joined” refers to configurations whereby an element is directly securedto another element by affixing the element directly to the other elementand to configurations whereby an element is indirectly secured toanother element by affixing the element to intermediate member(s) whichin turn are affixed to the other element.

“Film” refers to a sheet-like material wherein the length and width ofthe material far exceed the thickness of the material. Typically, filmshave a thickness of about 0.5 mm or less.

“Water-permeable” and “water-impermeable” refer to the penetrability ofmaterials in the context of the intended usage of disposable absorbentarticles. Specifically, the term “water-permeable” refers to a layer ora layered structure having pores, openings, and/or interconnected voidspaces that permit liquid water, urine, or synthetic urine to passthrough its thickness in the absence of a forcing pressure. Conversely,the term “water-impermeable” refers to a layer or a layered structurethrough the thickness of which liquid water, urine, or synthetic urinecannot pass in the absence of a forcing pressure (aside from naturalforces such as gravity). A layer or a layered structure that iswater-impermeable according to this definition may be permeable to watervapor, i.e., may be “vapor-permeable.” As is well known in the art, acommon method for measuring the permeability to water, urine, orsynthetic urine of the materials typically used in absorbent articles isa hydrostatic pressure test, also called a hydrostatic head test orsimply a “hydrohead” test. Suitable well known compendial methods forhydrohead testing are approved by INDA (formerly the InternationalNonwovens and Disposables Association, now The Association of theNonwoven Fabrics Industry) and EDANA (European Disposables And NonwovensAssociation).

“Extendibility” and “extensible” mean that the width or length of thecomponent in a relaxed state can be extended or increased.

“Elastic,” “elastomer,” and “elastomeric” refer to a material whichgenerally is able to extend to a strain of at least 50% without breakingor rupturing, and is able to recover substantially to its originaldimensions after the deforming force has been removed.

“Elastomeric material” is a material exhibiting elastic properties.Elastomeric materials may include elastomeric films, scrims, nonwovens,and other sheet-like structures.

“Outboard” and “inboard” refer respectively to the location of anelement disposed relatively far from or near to the longitudinalcenterline of the diaper with respect to a second element. For example,if element A is outboard of element B, then element A is farther fromthe longitudinal centerline than is element B.

“Pant” refers to disposable absorbent articles having a pre-formed waistand leg openings. A pant may be donned by inserting a wearer's legs intothe leg openings and sliding the pant into position about the wearer'slower torso. Pants are also commonly referred to as “closed diapers”,“prefastened diapers”, “pull-on diapers”, “training pants” and“diaper-pants.”

“Nonwoven” fabric or web means a web having a structure of individualfibers or threads that are interlaid, but not in a regular oridentifiable manner as in a knitted fabric. Nonwoven fabrics or webshave been formed from many processes such as, for example, meltblowingprocesses, spunbonding processes, air laying processes, and bondedcarded web processes. The basis weight of nonwoven fabrics is usuallyexpressed in ounces of material per square yard (osy) or grams persquare meter (gsm) and the fiber diameters are usually expressed inmicrons. (Note: to convert from osy to gsm, multiply osy by 33.91.)

“Woven” fabric or web means a fabric or web containing a structure offibers, filaments, or yarns, which are arranged in an orderly,inter-engaged fashion. Woven fabrics typically contain inter-engagedfibers in a warp and fill direction. The warp direction corresponds tothe length of the fabric while the fill direction corresponds to thewidth of the fabric. Woven fabrics can be made, for example, on avariety of looms including, but not limited to, shuttle looms, rapierlooms, projectile looms, air jet looms, and water jet looms.

“Spunbonded fibers”, or “spunbond fibers”, means small-diameter fibersthat are typically formed by extruding molten thermoplastic material asfilaments from a plurality of fine capillaries of a spinneret having acircular or other configuration, with the diameter of the extrudedfilaments then being rapidly reduced as by, for example, in U.S. Pat.Nos. 4,340,563, 3,692,618, 3,802,817, 3,338,992, 3,341,394, 3,502,763,3,502,538, and 3,542,615. Spunbond fibers are quenched and generally nottacky when they are deposited onto a collecting surface. Spunbond fibersare generally continuous and often have average diameters larger thanabout 7 microns, and more particularly between about 10 and 30 microns.A spunbond material, layer, or substrate comprises spunbonded (orspunbond) fibers.

The term “meltblown fibers” means fibers formed by extruding a moltenmaterial, typically thermoplastic in nature, through a plurality offine, usually circular, die capillaries as molten threads or filamentsinto converging high-velocity heated gas (e.g., air) streams thatattenuate the filaments of molten material to reduce their diameter,which may be to microfiber diameter. Thereafter, the meltblown fibersare carried by the high-velocity gas stream and are deposited on acollecting surface to form a web of randomly dispersed meltblown fibers.Such a process is disclosed for example, in U.S. Pat. No. 3,849,241.Meltblown fibers are microfibers which may be continuous ordiscontinuous, are generally smaller than 10 microns in diameter, andare generally self-bonding when deposited onto a collecting surface

The term “microfibers” means small-diameter fibers having an averagediameter not greater than about 100 microns, for example, having adiameter of from about 0.5 microns to about 50 microns, morespecifically microfibers may also have an average diameter of from about1 micron to about 20 microns. Microfibers having an average diameter ofabout 3 microns or less are commonly referred to as ultra-finemicrofibers. A description of an exemplary process of making ultra-finemicrofibers may be found in, for example, U.S. Pat. No. 5,213,881.

“Conventional hot-melt adhesive” means a formulation that generallycomprises several components. These components typically include one ormore polymers to provide cohesive strength (e.g., aliphatic polyolefinssuch as poly (ethylene-co-propylene) copolymer; ethylene vinyl acetatecopolymers; styrene-butadiene or styrene-isoprene block copolymers;etc.); a resin or analogous material (sometimes called a tackifier) toprovide adhesive strength (e.g., hydrocarbons distilled from petroleumdistillates; rosins and/or rosin esters; terpenes derived, for example,from wood or citrus, etc.); perhaps waxes, plasticizers or othermaterials to modify viscosity (i.e., flowability) (examples of suchmaterials include, but are not limited to, mineral oil, polybutene,paraffin oils, ester oils, and the like); and/or other additivesincluding, but not limited to, antioxidants or other stabilizers. Atypical hot-melt adhesive formulation might contain from about 15 toabout 35 weight percent cohesive strength polymer or polymers; fromabout 50 to about 65 weight percent resin or other tackifier ortackifiers; from more than zero to about 30 weight percent plasticizeror other viscosity modifier; and optionally less than about 1 weightpercent stabilizer or other additive. It should be understood that otheradhesive formulations comprising different weight percentages of thesecomponents are possible.

“Hot-melt processable” means that an adhesive composition may beliquefied using a hot-melt tank (i.e., a system in which the compositionis heated so that it is substantially in liquid form) and transportedvia a pump (e.g., a gear pump or positive-displacement pump) from thetank to the point of application proximate a substrate or othermaterial; or to another tank, system, or unit operation (e.g., aseparate system, which may include an additional pump or pumps, fordelivering the adhesive to the point of application). Hot-melt tanksused to substantially liquefy a hot-melt adhesive typically operate in arange from about 38° C. to about 230° C. Generally, at the point ofapplication, the substantially liquefied adhesive composition will passthrough a nozzle or bank of nozzles, but may pass through some othermechanical element such as a slot. A hot-melt processable adhesivecomposition is to be contrasted with a composition that requires aconventional extruder, and the attendant pressures and temperaturescharacteristic of an extruder, to liquefy, mix, and/or convey thecomposition. While a hot-melt tank and pump in a hot-melt processingsystem can handle adhesive-composition viscosities in a range from about1000 centipoise to about 10,000 centipoise, an extruder can handle andprocess adhesive-composition viscosities in a range from about 10,000centipoise to viscosities of several hundred thousand centipoise.

Unless otherwise noted, “Laminated structure” or “laminate” means astructure in which one layer, material, component, web, or substrate isadhesively bonded, at least in part, to another layer, material,component, web, or substrate. As stated elsewhere in this application, alayer, material, component, web, or substrate may be folded over andadhesively bonded to itself to form a “laminated structure” or“laminate.”

FIG. 1 is a plan view of an exemplary, non-limiting embodiment of adiaper 20 of the present invention in a flat, uncontracted state (i.e.,without elastic induced contraction). The garment-facing surface 120 ofthe diaper 20 is facing the viewer. The diaper 20 includes alongitudinal centerline 100 and a lateral centerline 110. The diaper 20may comprise a chassis 22. The diaper 20 and chassis 22 are shown tohave a front waist region 36, a rear waist region 38 opposed to thefront waist region 36, and a crotch region 37 located between the frontwaist region 36 and the rear waist region 38. The waist regions 36 and38 generally comprise those portions of the diaper 20 which, when worn,encircle the waist of the wearer. The waist regions 36 and 38 mayinclude elastic elements such that they gather about the waist of thewearer to provide improved fit and containment. The crotch region 37 isthat portion of the diaper 20 which, when the diaper 20 is worn, isgenerally positioned between the legs of the wearer.

The outer periphery of chassis 22 is defined by longitudinal side edges12 and end edges 14. The chassis 22 may have opposing longitudinal sideedges 12 that are oriented generally parallel to the longitudinalcenterline 100. However, for better fit, longitudinal side edges 12 maybe curved or angled to produce, for example, an “hourglass” shape diaperwhen viewed in a plan view. The chassis 22 may have opposing lend edges14 that are oriented generally parallel to the lateral centerline 110.

The chassis 22 may comprises a liquid permeable topsheet 24 havinglongitudinal side edges 25, a backsheet 26, and an absorbent core 28between the topsheet 24 and the backsheet 26. The absorbent core 28 mayhave a body-facing surface and a garment facing-surface. The topsheet 24may be joined to the core 28 and/or the backsheet 26. The backsheet 26may be joined to the core 28 and/or the topsheet 24. It should berecognized that other structures, elements, or substrates may bepositioned between the core 28 and the topsheet 24 and/or backsheet 26.In certain embodiments, the chassis 22 comprises the main structure ofthe diaper 20 with other features may added to form the composite diaperstructure. While the topsheet 24, the backsheet 26, and the absorbentcore 28 may be assembled in a variety of well-known configurations,preferred diaper configurations are described generally in U.S. Pat.Nos. 3,860,003; 5,151,092; 5,221,274; 5,554,145; 5,569,234; 5,580,411;and 6,004,306.

The topsheet 24 is generally a portion of the diaper 20 that may bepositioned at least in partial contact or close proximity to a wearer.Suitable topsheets 24 may be manufactured from a wide range ofmaterials, such as porous foams; reticulated foams; apertured plasticfilms; or woven or nonwoven webs of natural fibers (e.g., wood or cottonfibers), synthetic fibers (e.g., polyester or polypropylene fibers), ora combination of natural and synthetic fibers. The topsheet 24 isgenerally supple, soft feeling, and non-irritating to a wearer's skin.Generally, at least a portion of the topsheet 24 is liquid pervious,permitting liquid to readily penetrate through the thickness of thetopsheet 24. A particularly preferred topsheet 24 is available from BBAFiberweb, Brentwood, Tenn. as supplier code 055SLPV09U.

Any portion of the topsheet 24 may be coated with a lotion as is knownin the art. Examples of suitable lotions include those described in U.S.Pat. Nos. 5,607,760; 5,609,587; 5,635,191; and 5,643,588. The topsheet24 may be fully or partially elasticized or may be foreshortened so asto provide a void space between the topsheet 24 and the core 28.Exemplary structures including elasticized or foreshortened topsheetsare described in more detail in U.S. Pat. Nos. 4,892,536; 4,990,147;5,037,416; and 5,269,775.

The absorbent core 28 may comprise a wide variety of liquid-absorbentmaterials commonly used in disposable diapers and other absorbentarticles. Examples of suitable absorbent materials include comminutedwood pulp, which is generally referred to as air felt creped cellulosewadding; melt blown polymers, including co-form; chemically stiffened,modified or cross-linked cellulosic fibers; tissue, including tissuewraps and tissue laminates; absorbent foams; absorbent sponges;superabsorbent polymers; absorbent gelling materials; or any other knownabsorbent material or combinations of materials. These materials may becombined to provide a core 28 in the form of one or more layers(individual layers not shown) that may include fluid handling layerssuch as acquisition layers, distribution layers and storage layers. Suchabsorbent cores 28 may also include layers (not shown) to stabilizeother core components. Such layers include a core cover and a dustinglayer. A suitable material for such layers is aspunbonded/meltblown/spunbonded nonwoven having a basis weight betweenabout 10 and 15 g/m² (the meltblown layer comprises <5 g/m²) as isavailable from Avgol America, Inc. of Knoxville, N.C. For example,Exemplary absorbent structures for use as the absorbent core 28 aredescribed in U.S. Pat. Nos. 4,610,678; 4,673,402; 4,834,735; 4,888,231;5,137,537; 5,147,345; 5,342,338; 5,260,345; 5,387,207; 5,397,316; and5,625,222 and in published U.S. patent application Ser. Nos.04/0,162,536 and 04/0,167,486.

The backsheet 26 is generally positioned such that it may be at least aportion of the garment-facing surface 120 of the diaper 20. Backsheet 26may be designed to prevent the exudates absorbed by and contained withinthe diaper 20 from soiling articles that may contact the diaper 20, suchas bed sheets and undergarments. In certain embodiments, the backsheet26 is substantially water-impermeable. Suitable backsheet 26 materialsinclude films such as those manufactured by Tredegar Industries Inc. ofTerre Haute, Ind. and sold under the trade names X15306, X10962, andX10964. Other suitable backsheet 26 materials may include breathablematerials that permit vapors to escape from the diaper 20 while stillpreventing exudates from passing through the backsheet 26. Exemplarybreathable materials may include materials such as woven webs, nonwovenwebs, composite materials such as film-coated nonwoven webs, andmicroporous films such as manufactured by Mitsui Toatsu Co., of Japanunder the designation ESPOIR NO and by EXXON Chemical Co., of Bay City,Tex., under the designation EXXAIRE. Suitable breathable compositematerials comprising polymer blends are available from ClopayCorporation, Cincinnati, Ohio under the name HYTREL blend P18-3097. Suchbreathable composite materials are described in greater detail in PCTApplication No. WO 95/16746 and U.S. Pat. No. 5,865,823. Otherbreathable backsheets including nonwoven webs and apertured formed filmsare described in U.S. Pat. No. 5,571,096. An exemplary, suitablebacksheet is disclosed in U.S. Pat. No. 6,107,537. Other suitablematerials and/or manufacturing techniques may be used to provide asuitable backsheet 26 including, but not limited to, surface treatments,particular film selections and processing, particular filamentselections and processing, etc.

Backsheet 26 may also consist of more than one layer, as illustrated inthe cut-away of FIG. 1. The backsheet 26 may comprise an outer cover 26a and an inner layer 26 b. The outer cover 26 a may have longitudinalside edges 27 a and the inner layer 26 b may have longitudinal sideedges 27 b. The outer cover 26 a may be made of a soft, non-wovenmaterial. The inner layer 26 b may be made of a substantiallywater-impermeable film. The outer cover 26 a and an inner layer 26 b maybe joined together by adhesive or any other suitable material or method.A particularly suitable outer cover 26 a is available from Corovin GmbH,Peine, Germany as supplier code A18AH0, and a particularly suitableinner layer 26 b is available from RKW Gronau GmbH, Gronau, Germany assupplier code PGBR4WPR. While a variety of backsheet configurations arecontemplated herein, it would be obvious to those skilled in the artthat various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention.

The diaper 20 may also include a fastening system 50. When fastened, thefastening system 50 interconnects the front waist region 36 and the rearwaist region 38 resulting in a waist circumference that may encircle thewearer during wear of the diaper 20. The fastening system 50 maycomprises a fastener such as tape tabs, hook and loop fasteningcomponents, interlocking fasteners such as tabs & slots, buckles,buttons, snaps, and/or hermaphroditic fastening components, although anyother known fastening means are generally acceptable. Some exemplarysurface fastening systems are disclosed in U.S. Pat. Nos. 3,848,594;4,662,875; 4,846,815; 4,894,060; 4,946,527; 5,151,092; and 5,221,274. Anexemplary interlocking fastening system is disclosed in U.S. Pat. No.6,432,098. The fastening system 50 may also provide a means for holdingthe article in a disposal configuration as disclosed in U.S. Pat. No.4,963,140. The fastening system 50 may also include primary andsecondary fastening systems, as disclosed in U.S. Pat. No. 4,699,622.The fastening system 50 may be constructed to reduce shifting ofoverlapped portions or to improve fit as disclosed in U.S. Pat. Nos.5,242,436; 5,499,978; 5,507,736; and 5,591,152.

FIG. 1 depicts a fastening system 50 having an engaging member 52 and areceiving member 54. The engaging member 52 is shown having an engagingsurface 53 that may comprise hooks, loops, an adhesive, a cohesive, orother fastening member. The receiving member 54 may have a surface thatallows for engagement of the engaging member 52. The receiving member 54may comprise hooks, loops, an adhesive, a cohesive, or other fasteningcomponent that can receive the engaging member 52. Suitable engagingmember 52 and receiving member 54 combinations include but are notlimited to hooks/loop, hooks/hooks, adhesive/polymeric film;cohesive/cohesive, adhesive/adhesive; tab/slot; and button/button hole.

The diaper 20 may include barrier cuffs 60 and/or gasketing cuffs 70.Gasketing cuffs 70 may also be referred to as outer leg cuffs, legbands, side flaps, leg cuffs, or elastic cuffs. Barrier cuffs 60 mayalso be referred to as second cuffs, inner leg cuffs or “stand-up”elasticized flaps.

The gasketing cuff 70 may be substantially inelastic or may beelastically extensible to dynamically fit at the wearer's leg. Thegasketing cuff 70 may be formed by one or more elastic members 72 (suchas elastic strands) operatively joined to the topsheet 24, backsheet 26,or any other suitable substrate used in the formation of the diaper 20.Suitable gasketing cuff construction is further described in U.S. Pat.No. 3,860,003

The barrier cuff 60 may have a distal edge 61 and a proximal edge 63that run substantially parallel to the longitudinal centerline 100. Thebarrier cuff 60 may span the entire longitudinal length of the diaper20. The barrier cuff 60 may be formed by a flap 62 and an elastic member64 (such as elastic strands). The flap 62 may be a continuous extensionof any of the existing materials or elements that form the diaper 20. Inother embodiments, such as shown in FIG. 1, the barrier cuff 60 may be adiscrete element. In such embodiments, the barrier cuff 60 comprisingthe flap 62 and the elastic member 64 may be formed then joined to thechassis 22 by a bond 65.

The flap 62 may comprise a variety of substrates such as plastic filmsand woven or nonwoven webs of natural fibers (e.g., wood or cottonfibers), synthetic fibers (e.g., polyester or polypropylene fibers), ora combination of natural and synthetic fibers. In certain embodiments,the flap 62 may comprise a nonwoven web such as spunbond webs, meltblownwebs, carded webs, and combinations thereof (e.g., spunbond-meltblowncomposites and variants). Laminates of the aforementioned substrates mayalso be used to form the flap 62. A particularly suitable flap maycomprise a nonwoven available from BBA Fiberweb, Brentwood, Tenn. assupplier code 30926. A particularly suitable elastic member is availablefrom Invista, Wichita, Kans. as supplier code T262P. Further descriptionof diapers having barrier cuffs and suitable construction of suchbarrier cuffs may be found in U.S. Pat. Nos. 4,808,178 and 4,909,803.The elastic member 64 generally spans the longitudinal length of thebarrier cuff 60. In other embodiments, the elastic member 64 may span atleast the longitudinal length of the barrier cuff 60 within the crotchregion 37. It is desirable that the elastic member 64 exhibitssufficient elasticity such that the proximal edge 63 of the barrier cuff60 remains in contact with the wearer during normal wear, therebyenhancing the barrier properties of the barrier cuff 60. The elasticmember 64 may be connected to the flap 62 at opposing longitudinal ends.In certain embodiments, the flap 62 may be folded over onto itself so asto encircle the elastic member 64. A bond 67 may be used to secure thefolded section of the flap 62.

The barrier cuffs 60 and/or gasketing cuffs 70 may be treated, in fullor in part, with a lotion, as described above with regard to topsheets,or may be fully or partially coated with a hydrophobic surface coatingas detailed in U.S. application Ser. No. 11/055,743, which was filedFeb. 10, 2005.

The diaper 20 may include front ears 40 and back ears 42. The frontand/or back ears 40, 42 may be unitary elements of the diaper 20 (i.e.,they are not separately manipulative elements secured to the diaper 20,but rather are formed from and are extensions of one or more of thevarious layers of the diaper). In certain embodiments, the front and/orback ears 40, 42 may be discrete elements that are joined to the chassis22, as shown in FIG. 1. Discrete front and/or back ears 40, 42 may bejoined to the chassis 22 by any bonding method known in the art such asadhesive bonding, pressure bonding, heat bonding, and the like. In otherembodiments, the front and/or back ears 40, 42 may comprise a discreteelement joined to the chassis 22 with the chassis 22 having a layer,element, or substrate that extends over the front and/or back ear 40,42. The front ears 40 and back ears 42 may be extensible, inextensible,elastic, or inelastic. The front ears 40 and back ears 42 may be formedfrom nonwoven webs, woven webs, knitted fabrics, polymeric andelastomeric films, apertured films, sponges, foams, scrims, andcombinations and laminates thereof. In certain embodiments the frontears 40 and back ears 42 may be formed of a nonwoven/elastomericmaterial laminate or a nonwoven/elastomeric material/nonwoven laminate.A suitable elastic back ear 42 may be a laminate comprising anelastomeric film (such as is available from Tredegar Corp, Richmond,Va., as supplier code X25007) disposed between two nonwoven layers (suchas is available from BBA Fiberweb, Brentwood, Tenn. as supplier codeFPN332). While the following embodiments are directed to back ear 42design and construction, these embodiments are equally applicable tofront ear 40 design and construction. It should be recognized that anycombination of the following embodiments may be used for the back ear 42and/or the front ear 40.

In alternative embodiments, the diaper 20 may be preformed by themanufacturer to create a pant. A pant may be preformed by any suitabletechnique including, but not limited to, joining together portions ofthe article using refastenable and/or non-refastenable bonds (e.g.,seam, weld, adhesive, cohesive bond, fastener, etc.). For example, thediaper 20 of FIG. 1 may be manufactured with the fastening system 50engaged (i.e., the engaging member 52 is joined to the receiving member54). As an additional example, the diaper 20 of FIG. 1 may bemanufactured with the front ears 40 joined to the back ears 42 by way ofa bond such as an adhesive bond, a mechanical bond, or some otherbonding technique known in the art. Suitable pants are disclosed in U.S.Pat. Nos. 5,246,433; 5,569,234; 6,120,487; 6,120,489; 4,940,464;5,092,861; 5,897,545; and 5,957,908.

As noted above, a construction adhesive is typically used to joincomponents of an absorbent article as the absorbent article is beingassembled. Nonlimiting examples of such joinder using the constructionadhesive include but are not limited to:

-   -   core cover to dusting layer sealing;    -   backsheet 26 to core 28;    -   elastic member 64 to nonwoven and/or film to form a barrier cuff        60 or a gasketing cuff 70.    -   nonwoven to vapor permeable film to form a backsheet 26;    -   barrier cuffs to topsheet 24;    -   receiving member 54 to topsheet 24;    -   ear 40, 42 to backsheet 26.

As will be recognized, many of these uses involve joinder of a nonwovenmaterial to another material. As will be further recognized, if theconstruction adhesive is too fluid for the time scale of the operation,it can flow through the nonwoven material with deleterious effect onprocess performance or product perception.

In one example, if the open time of the construction adhesive is toolong, the adhesive may remain flowable and tacky after the twocomponents to be joined have passed from the joinder unit operation onthe assembly process to a subsequent unit operation in the process. Insome instances such a downstream process may put a force on the adhesivecausing it to flow through the nonwoven material. For example, if thenonwoven material passes over a roll, web tension can cause pressure onthe nonwoven causing a flowable adhesive to flow into and even throughvoid space in the nonwoven. If the adhesive reaches the surface of thenonwoven that contacts the roll portion of the adhesive can transfer tothe roll with resulting contamination thereof. Such contamination cancause substantial operational problems (e. g. roll wrapping) to a webbased assembly process.

In another example, if the viscosity at ambient conditions (e. g. lessthan about 40° C.) is too low the pressure caused by the compressionpackaging typically used for absorbent articles can provide a drivingforce to cause a portion of the construction adhesive to flow into andeven through the void volume of a nonwoven material (It should berecognized that too low is a relative term and the absolute viscositycan be quite high and still flow into a nonwoven due to the relativelylong time scale). If the adhesive reaches an outer surface of thenonwoven material it can act to join any adjacent material thereto. Forexample, the construction adhesive (not shown) used to join the elasticmember 64 of barrier cuff 60 to the nonwoven material comprising flap 62may flow through the nonwoven material causing barrier cuff 60 to adhereto topsheet 24. If such adherence occurs, a user (e. g. a caregiver foran infant) may have difficulty opening the diaper for application to awearer. The In Bag Compression Opening Test described in the TESTMETHODS section below simulates the opening of an absorbent article foruse and provides a measure of any force causing components of theabsorbent article to adhere to each other with a resulting increase inopening difficulty.

It has been surprisingly found that increasing the crystallization rateof the polymeric material comprising the construction adhesive providesan unexpected reduction in such opening force. As can be seen from theEXAMPLE below and in FIG. 2, adding an effective amount of acrystallization facilitator can provide a marked decrease in the productopening force as measured by the In Bag Compression Opening Test. Asused herein an effective amount of a crystallization enhancer is thequantity required to cause the opening force of a product assembledusing a construction adhesive comprising the crystallization enhancer tobe less than 0.75N as measured by the In Bag Compression Opening Test.Preferably, the opening force is less than about 0.6N, more preferablyless than about 0.5N. Suitable crystallization enhancers include, butare not limited to microcrystalline waxes and crystalline olefinhomopolymers. Particularly preferred is a linear polyethylenehomopolymer. Without being bound by theory it is believed that suchmaterials crystallize more readily as temperature decreases due tominimal branching. The crystallites thus formed then serve as a templatefor crystallization of the polymeric material.

As is known, hot melt adhesives can comprise a wide variety of basepolymers. Suitable materials for formulation of hot melt adhesivesinclude, but are not limited to polyethylene; ethylene vinyl acetate;block copolymer elastomers (e. g. styrene-isoprene-styrene (SIS) andstyrene-butadiene-styrene (SBS)) and amorphous polyolefins (e. g.atactic polypropylene). Hot melt adhesives formulated from some of thesebase polymers can even have a desirably low opening force. For example,the styrene-isoprene-styrene based hot melt formulation (H1358 as isavailable from H. B. Fuller Company of St. Paul, Minn.) described in theEXAMPLE has an opening force of about 0.5N. However, the susceptibilityof block copolymer based adhesives to oxidation is well known (Withoutbeing bound by theory such susceptibility is believed to be due toresidual unsaturation in the polymer backbone which is susceptible todegradation). Preferred hot melt adhesives for purposes the presentinvention are those formulations based on an ethylene interpolymer witha C₃-C₂₀ α olefin as are generally described in published PCTapplication WO 97/33921. Particularly preferred resin comprising suchpolymers are interpolymers of ethylene and 1-octene marketed by the DowChemical Company of Midland, Mich. under the trade name Affinity. Suchformulations provide desirable oxidation resistance because they arebelieved to have less residual unsaturation and can be modified byappropriate choice of a crystallization enhancer so as to provideabsorbent articles having the low opening force of the presentinvention. A particularly preferred hot melt adhesive formulation foruse as a construction adhesive to provide absorbent articles accordingto the present invention is D3166 as is available from H. B. FullerCompany.

The construction adhesive can be applied using a wide variety of knownapplication methods including but not limited to slot extrusion, sprays,including spiral sprays, and beads. Specific examples include but arenot limited to:

-   -   application of the construction adhesive in a spiral spray or        slot coating to join a topsheet to an underlying nonwoven layer;    -   application of the construction adhesive via slot coating to        join an acquisition layer or a distribution layer to a core        cover;    -   application of beads of the construction adhesive located        between the nonwoven material comprising the cuff and the        backsheet;    -   application of the construction adhesive in a spiral spray or        slot coating to join the topsheet to the backsheet so as to seal        the longitudinal edges of the absorbent article;    -   application of the construction adhesive using slot coating to        join a landing zone (i. e. a receiving member) to the backsheet;    -   application of the construction adhesive using slot coating to        join the core cover to the dusting layer;    -   application of the construction adhesive in a spiral spray to        join the core to the backsheet.    -   application of the construction adhesive in a spiral spray to        join the nonwoven material comprising the cuff to the nonwoven        material comprising the backsheet.

In order to be hot melt processable so as to enable application of theconstruction adhesive, the adhesive must be heated to a temperature highenough so as to insure the adhesive flows readily but not so hot so asto cause degradation of the adhesive at an unacceptable rate. Suitably,the adhesive is maintained at a temperature between about 100° C. andabout 230° C. before application. Preferably the adhesive is maintainedat a temperature between about 120° C. and about 200° C.

Test Methods In Bag Compression Opening Force Test Sample Preparation

-   1. Assemble finished absorbent articles using the construction    adhesive to be evaluated and pack into commercially sized packaging.-   2. Store the packed absorbent articles at 60° C.±2° C. for 3 days    using a suitable means (e. g. a laboratory oven.-   3. Remove the packed absorbent articles from 60° C. storage and    allow to equilibrate at 25° C.±2° C.-   4. Open the packaging and carefully remove at least 5 absorbent    articles per evaluation therefrom taking care not to disturb any    bonding between surfaces.

Opening Force Measurement Apparatus

-   Tensile Tester: A suitable instrument is available from MTS Systems    of Eden Prairie Minn. as a model Q Test/1 L or equivalent-   Load Cell: 100N; MTS Part No. 450100818-   Jaws: 25×75 mm with rubber grips; MTS Part No. 56-163-815 or    equivalent-   Interface Software: Test Works 4 from MTS or equivalent. Set up to    acquire force/extension data from the tensile tester.-   Personal Computer: Suitable system for running the interface    software

Setup

Crosshead Speed 300 mm/min Gage Length  60 mm Stop Length 120 mm

Operation

-   1. Set up and calibrate the tensile tester according to the    manufacturer's instructions.-   2. Carefully unfold any longitudinal folds so as to expose one of    the ears of the sample absorbent article.-   3. Partially unfold, insert and clamp the distal edge of the ear of    the sample into the upper jaw taking care not to disturb any    adhesion that may be present between components of the absorbent    article.-   4. Carefully insert and clamp the folded opposing ear into the lower    jaw of the tensile tester insuring that there is slight slack in the    clamped sample.-   5. Initiate the extension cycle of the tensile tester-   6. The opening force is defined as the peak force observed during    the 60 mm extension cycle.-   7. Repeat steps 2-6 for at least 4 additional samples.

Calculation and Reporting

-   1. Determine the average and standard deviation of the individual    opening forces measured as described above.-   2. Report the mean opening force for each absorbent article type    evaluated and the related standard deviation.

EXAMPLE

This example is intended to show the mean opening force for constructionadhesives used to assemble absorbent articles.

Infant diapers were produced on a standard diaper production line usingthree different construction adhesives. Table 1 describes the adhesivesand the results of opening force evaluation.

TABLE 1 In Bag Compression Opening Force for Various ConstructionAdhesives Construction Adhesive Type A B Polyolefin Based PolyolefinBased Not of the According to the C Invention¹ Invention² SIS Based³Mean  1.2N  0.5N  0.5N Standard 0.47N 0.10N 0.11N Deviation ¹Size 5infant diaper assembled using construction adhesive D3155 as isavailable from H. B. Fuller Company of St. Paul, MN ²Size 5 infantdiaper assembled using construction adhesive D3166 as is available fromH. B. Fuller Company of St. Paul, MN ³Size 4 infant diaper assembledusing construction adhesive H1358LOF as is available from H. B. FullerCompany of St. Paul, MN

FIG. 2 shows a representative stress strain curve (F is force in Newtonsand E is extension in mm) for measurement of the opening force for adiaper assembled using each of the construction adhesives where 210 isthe curve for adhesive A, 220 is the curve for adhesive B and 230 is thecurve for adhesive C. As can be seen the construction adhesive used toassemble diapers according to the present invention and the diapersassembled using the SIS construction adhesive have very comparable meanopening forces while the diapers assembled using the other polyolefinbased adhesive has an opening force nearly three times as large.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A disposable absorbent article comprising: a) atopsheet, a backsheet underlying the topsheet, and an absorbent coredisposed between the topsheet and the backsheet; and b) apolyolefin-based construction adhesive suitable for joining an absorbentarticle component comprising a nonwoven material and another absorbentarticle component together, wherein the adhesive comprises a linearpolyethylene homopolymer; wherein the absorbent article has an in-bagcompression opening force of less than about 0.75N.
 2. The absorbentarticle according to claim 1, wherein the adhesive is maintained at atemperature from about 100° C. to about 230° C. before application. 3.The absorbent article according to claim 1, wherein the adhesive furthercomprises an atactic polypropylene and polybutene.
 4. The absorbentarticle according to claim 1, wherein the opening force is less thanabout 0.6N.
 5. The absorbent article according to claim 1, wherein theconstruction adhesive joins a core cover to an absorbent articlecomponent selected from the group consisting of: the backsheet, anacquisition layer, a distribution layer, and a dusting layer.
 6. Theabsorbent article according to claim 1, wherein the constructionadhesive joins the backsheet to an absorbent article component selectedfrom the group consisting of: a receiving member, a dusting layer, andan elastic material.
 7. The absorbent article according to claim 1,wherein the construction adhesive joins the topsheet to: (a) thebacksheet adjacent a longitudinal edge of the absorbent article; (b) anunderlying nonwoven layer; or (c) both.
 8. The absorbent articleaccording to claim 1, wherein the construction adhesive joins an elasticmaterial to a nonwoven material to form a barrier cuff.
 9. The absorbentarticle according to claim 1, wherein the absorbent article is a diaper.10. The absorbent article according to claim 1, wherein the absorbentarticle is a training pant.
 11. A method of assembling an absorbentarticle comprising the steps of: a) providing a polyolefin-basedconstruction adhesive wherein the adhesive comprises a linearpolyethylene homopolymer; b) providing an absorbent article componentcomprising a nonwoven material and a plurality of other absorbentarticle components; and c) joining the absorbent article componentcomprising a nonwoven material to at least one of the other absorbentarticle components using the polyolefin-based construction adhesive soas to assemble the absorbent article whereby the absorbent article hasan in-bag compression opening force of less than about 0.75N.
 12. Themethod according to claim 11, wherein the adhesive is maintained at atemperature from about 100° C. to about 230° C. before application. 13.The method according to claim 11, wherein the adhesive further comprisesan atactic polypropylene and polybutene.
 14. The method according toclaim 11, wherein the opening force is less than about 0.6N.
 15. Themethod according to claim 11, wherein step c comprises the step ofjoining a core cover to an absorbent article component selected from thegroup consisting of: the backsheet, an acquisition layer, a distributionlayer, and a dusting layer.
 16. The method according to claim 11,wherein step c comprises the step of joining the backsheet to anabsorbent article component selected from the group consisting of: areceiving member, a dusting layer, and an elastic material.
 17. Themethod according to claim 11, wherein step c comprises the applicationof the construction adhesive in a spiral spray or slot coating to join atopsheet to an underlying nonwoven layer.
 18. The method according toclaim 11, wherein step c comprises the application of the constructionadhesive via slot coating to join an acquisition layer or a distributionlayer to a core cover.
 19. The method according to claim 11, whereinstep c comprises the application of beads of the construction adhesivelocated between the nonwoven material comprising the cuff and thebacksheet.
 20. The method according to claim 11, wherein step ccomprises the application of the construction adhesive in a spiral sprayor slot coating to join the topsheet to the backsheet so as to seal thelongitudinal edges of the absorbent article.